The subject matter disclosed herein generally relates to engine starter systems, and more specifically to interfacing a reduction gear train for a core-turning motor with a starter of a gas turbine engine.
Modern aircraft gas turbine engines operate with relatively small radial clearances in order to optimize the efficiency of the engine. When such an engine is shut down, heat from the engine core rises to the top of the engine case, and this uneven distribution of heat can result in the engine rotor axis bending or “bowing”. If an engine is re-started in this condition, it can result in potential damage or reduced performance. One potential solution to this is to rotate the engine at very low speed after it is turned off. By allowing the rotor to rotate slowly, heat is dissipated evenly and rotor bow can be minimized. A pneumatic turbine starter can be used to both start and motor (i.e., turn at a speed less than the starting speed) the engine using available compressed air from a variety of sources. However, both an air valve used to regulate the compressed air supplied to the starter and the starter itself are typically designed primarily for short duration transient operations, not continuous motoring at low speeds. Regulating the air supply and operating at moderate torque and speeds of normal engine motoring can be detrimental to the life of the air valve and starter.